Designing Wind Resistant Complex Facades and Rooftop Equipment

TESTING PROVIDES EMPIRICAL EVIDENCE FOR ENGINEERING CALCULATIONS AS WELL AS FINDS POTENTIAL WEAK POINTS THAT ARE EITHER OVERLOOKED OR IMPOSSIBLE TO FORESEE WITH ENGINEERING ANALYSIS

Architectural testing has evolved to become a necessary requirement for multiple types of openings and cladding – why not rooftop equipment and complex facades? Testing provides empirical evidence for engineering calculations as well as finds potential weak points that are either overlooked or impossible to foresee with engineering analysis. These may include:

FEMA, Rooftop equipment failures from Hurricane Katrina, Mississippi

For structural performance, ASTM E330 is used for windows, doors, skylights, and curtain walls. This uniform static air pressure difference structural testing, in addition to ASTM E1886 and E1996 impact and cyclic pressure testing, provides valuable data to ensure engineering analysis is correct and the units are performing as required.

For metal wall and roof panels, ASTM E1592 can be used to test for structural performance.

Roof membranes can be tested for uplift resistance using ASTM E907.

The desire for hurricane level wind resistance has caused test standards to be created for the majority of architectural components and cladding.

WHEN TESTING STANDARDS ARE NOT AVAILABLE OR APPLICABLE

Other equipment and components that are subjected to wind loads on buildings do not currently have test standards to ensure these features perform as intended. At the rooftop this includes equipment such as HVAC and photovoltaic systems as well as duct or pipe chases that are installed across the roof. Walls, signage, light fixtures, and some architectural features like fins and sunshades, don’t have a standard for structural performance testing. Free standing signs also do not have a way to test structural performance, and creating a test standard for all of these different pieces of equipment and components would be difficult. The reason for this is that an engineer’s judgment comes into play when deciding what testing should be performed for those things of which they are unsure. These decisions may be minor such as movement or vibration, which can cause wear or damage over time. Although not evident at first glance, an engineer may find these unacceptable, so the standard would have to be adapted for the particular component and method of testing.

Repair of architectural features

The reason a test standard would be helpful is that components, such as rooftop units (RTUs) or those attached to curtain wall systems, including fins and sunshades, are typically a delegated design, which have no structural test standard. What this means is that the structural engineer and architect pass the responsibility for ensuring these components meet wind loads to the designers of these components. RTUs are designed by mechanical engineers, where the most important factors are mechanical functions (as it should be). Typically these engineers do not take into consideration the high wind load potential on a roof. Roofing contractors will attach blocking and possibly attach the RTUs, but the wind resistance of the RTU itself is the responsibility of the manufacturer. Some types of RTUs may require additional mechanical anchors, such as cables or frames, to transfer the wind loads to the structure.

The International Building Code (IBC) and American Society of Civil Engineers (ASCE 7) have had significant changes in the recent editions to give increased attention to rooftop equipment, as many severe wind events have caused failures in this area. For rooftop equipment, IBC now requires the use of ASCE 7, and the 2010 edition of ASCE 7 now includes vertical uplift loads as well as the horizontal loads on RTUs.

RTUs can have issues from wind loads that aren’t captured in the required calculations from Chapter 29 of ASCE 7-10. For instance, vibrations can cause the unit to become unbalanced, which will lead to inefficiency and can eventually compromise the attachment. It is difficult to foresee or design for all of the possible incidents and predict the failures that can occur from wind loading without physically testing the units. Studies from wind tunnel testing have shown that different vent styles, and elevating the unit heights above the roof, can have a greater impact on wind loads than location on the roof alone. Another item the code doesn’t currently address is windscreens. Althcameronough testing has been performed that confirms windscreens will reduce loading on rooftop equipment when properly designed, the IBC code section 1609.1 states “Decreases in wind loads shall not be made for the effect of shielding by other structures.”

Corrosion, improper placement in slot, incorrect fastener

Physical testing currently on RTUs involves either model or full-scale wind tunnel tests. These give valuable information on structural performance of RTUs which can be used to design the components and attachment, as well as similar RTUs. Other rooftop components, such as satellite dishes, antennas, and piping with supports, should also go through some form of testing to give backup for engineers to consider when designing mountings or attachments for these different components in high wind zones.

WINDOW FINS AND SUNSHADES

Architectural features like window fins and sunshades are being used more recently as facades are becoming more complex. These features provide shade and thus control solar energy as well as
provide aesthetics. Structural failures with these components can cause safety concerns for people on the streets and sidewalks below. Although widely used, these components are typically unique to each project; therefore, little guidance is found in curtain wall literature or building codes. Manufacturers may provide load tables or general calculations, but it isn’t always clear to a designer what engineering has been done to back up that information. The wind loads acting on these flexible and lightweight shades and fins are difficult to estimate or even measure with a traditional pressure tap in a wind tunnel test. More recent studies have used hot-wire anemometry to perform wind tunnel tests and provide a better estimate on the attachment loads that are away from the building. Finally, testing on heavy components, such as glass features, is helpful to ensure the engineers understand how the fin behaves with high wind loads. During testing, vibration and permanent deformation may help the engineer refine the design of attachment components to prevent failures in the field.

CONSIDERATIONS FOR COASTAL WINDS

Aside from high wind loads caused by building height, many high wind loads observed on these architectural features are due to their proximity to the coast. In this location, designers will also observe more intense and frequent rain events as well as sea spray causing corrosion from the salt in the air. Corrosion resistance is important to assure attachment strength and prevent failures over time. Note that using 304 or 316 grade stainless steel fasteners are required by some code revisions in coastal areas.

THERMAL EXPANSION AND CONTRACTION OF METALS

Another design issue is thermal expansion and contraction of metals on these exterior features. Rigid attachment over long spans will end up shearing screws away when the temperature swings.
Slotted holes and plastic washers can be used to provide relief from the internal stresses that build up from thermal expansion and contraction on fasteners. Good workmanship is needed to attach
these “miscellaneous” building elements. In addition, anchors must be centered on slotted holes to perform properly, and tightening nuts with a torque wrench is usually necessary to achieve a precise tightness.

Z6 Commissioning performing roof membrane uplift resistance testing

Signage and lighting are also exterior building components that are difficult to estimate wind loads and do not have a standard test for wind resistance. Signage often fails in a major windstorm and the components can become dangerous projectiles. Exterior lighting attached to the building isn’t called out directly in the scope within ASCE 7 Chapter 29 for wind loads on building appurtenances, but it is assumed the solid attached signs method can be used to estimate wind loads on these components. Although attachments can be engineered, the light itself must be able to withstand higher wind loads, which is typically handled by the manufacturer.

CONCLUSION

Developing a test standard that could be used on such a wide range of building components would be difficult, but having actual test data for different types of sunshades, fins, and RTUs for engineers to reference and use in their design of similar components would be helpful. In many cases, such as custom signage, identical configurations could be used worldwide near coasts or high winds, and would be worth having a tested assembly. The test standard would likely require different parts for different types of these miscellaneous building components, and would most likely have different types of apparatus to apply the loading. For architectural testing companies, equipment such as wind generators, deflection gauges, load cells, mock-up walls and roofs are used regularly; however, since standards do not exist for these components, engineers typically have to come up with an improvised test to see how their building components perform.

15 years ago today, Billy Coltzer got this wild hair and thought…let’s open a building envelope consulting firm! My, how far we've come since then! Huge thanks to our hardworking team, incredible partners and clients for making this possible! We couldn't have done it without you! Let's keep growing! #Anniversary ... See MoreSee Less

The RCI, Inc. 33rd International Convention & Trade Show in Houston starts next week! Stop by Booth 221 to learn how Z6 can work with you to provide building envelope performance assurance and discove...

Our February Newsletter is available now! Stay updated on the latest Zero/Six news, industry-related topics and more - bit.ly/2BTlbP2! Did you miss a Newsletter? Check out previous editions - bit.ly/2Fz0dor

In this issue:• Ask Our Experts: Stormwater Authority• At-A-Glance: A Snapshot of Zero/Six Projects• Project Spotlight: UT System Replacement Office Building• Out & About: On the Move with the Zero/Six Team• Save the Date: RCI 2018• Zero/Six Employment Opportunities ... See MoreSee Less

The Zero/Six team was on a site visit to observe construction at UTRGV - The University of Texas Rio Grande Valley's Interdisciplinary Engineering & Academic Building (EIEAB) in Edinburg, TX. The facility will include six engineering teaching labs, two discipline-specific computer labs, eight 60-seat general classrooms, and offices and support spaces. Zero/Six’s scope of work encompasses a variety of envelope services throughout the design, construction and commissioning phases, including drawing review at four stages, submittal review, QA/QC services throughout the construction of the building envelope, and performance testing of fenestrations and roofing systems once completed. #EnvelopeArchitecture #WeKeeptheOutsideOut #QualityAssurance ... See MoreSee Less

We're excited to be at the Texas A&M University Construction Science Career Fair today & looking to #HireAggies! Stop by, say hello, and learn more about working for Zero/Six! #gigem #EnvelopeArchitec...

We're excited to be at the Texas A&M University Construction Science Career Fair today & looking to #HireAggies! Stop by, say hello, and learn more about working for Zero/Six! #gigem #EnvelopeArchitecture ... See MoreSee Less

Site visit! Assistant Project Manager, Zach Johnson, was on-site at UTMB Health's League City Campus Hospital to perform an envelope installation progress inspection. The phase II expansion includes construction of a five-story South Tower—which will add 123,000-square-feet to the hospital and a seven-story parking garage with an attached 33,000-square-foot multi-use building and connecting bridge. #WeKeeptheOutsideOut #QualityControl #BuildingEnvelope ... See MoreSee Less

Site Visit! Our Assistant Project Manager, Eddie Solis, is at UTRGV - The University of Texas Rio Grande Valley's Academic Building in Brownsville, TX to verify as-built systems are installed in accordance with the design intent and to resolve any field issues to ensure an air and watertight envelope is achieved. #WeKeeptheOutsideOut #BuildingEnvelope #QualityAssurance ... See MoreSee Less

Z6 Commissioning, LLC Launches New Company Division and Names Scott Leimer, P.E. as Vice President. From small site-specific projects to county or region-wide assessments, Z6 now has the ability to ad...

Zero/Six Consulting employees are our most important asset and it is with great pleasure that we announce the promotion of Nicole Ashline Gavin to Senior Vice President. Nicole is the classic example of the cream rising to the top no matter where it is placed. She first started working for Zero/Six shortly after Hurricane Ike as part-time administrative help; her desire to learn our business and her willingness to always help others has made her an irreplaceable part of the Z6 family. We are excited to walk into our 15th year with Nicole at the helm. Congratulations! You have earned it! #Proud2BeZ6 #WellDeserved #Z6Unstoppable ... See MoreSee Less

Forensic Supervisor Russell Hargett and Building Envelope Specialist Aaron Shaffner conducted a forensic investigation on a 13-story building in Houston to determine the source of reported water infiltration. The investigation included a rope access façade inspection, roof inspection, as well as diagnostic water testing per AAMA 501.2 at selected exterior transitions and glazing interfaces. Our team will issue a report that outlines investigation findings, testing procedures and results, observations, and recommendations for the best path forward in remediation. #EnvelopeArchitecture #WeKeeptheOutsideOut #BuildingScience ... See MoreSee Less

Many milestones have been achieved during 2017, we’ve turned 15 as a company and recently promoted Daniel Hodge as our firms first Associate Principal since Zero/Six Consulting’s founding in 2003. For 10 years, Daniel’s expertise has produced high performing teams and delivered exceptional results that have been integral in advancing our company’s strategic initiatives and growth. Congrats, Daniel! Much deserved. #Z6historymade #growwithus ... See MoreSee Less

From our Zero/Six Consulting family to yours, we want to wish you a wonderful holiday season with family and friends and a healthy and prosperous New Year. We'll see you in 2018! ... See MoreSee Less

From our @[721970454538155:274:Zero/Six Consulting] family to yours, we want to wish you a wonderful holiday season with family and friends and a healthy and prosperous New Year. We'll see you in 201...

As we come to the end of the year, Zero/Six Consulting President Billy Coltzer reflects on the impact of Hurricane Harvey and the unprecedented relief efforts and heroism exhibited by our employees, partners, and friends - “At a time when it really mattered (with cameras rolling), the world saw the best of Texas; no one needed to tell Texans (or the Cajuns!) that all lives are precious and deserve preservation.” Read more - bit.ly/2C5Twf3... See MoreSee Less

A Message from Our President: After the Storm - We have all seen the videos and heard the stories of how folks of varying points of view set their differences aside to help one another during, and aft...

Zero/Six Consulting is excited for 2018 and the new projects on the horizon– we're looking for fresh insight, creative minds and bold talent to work on unique projects in a wide variety of markets from design through project completion. Our corporate culture supports career advancement in an energetic, collaborative environment where innovation thrives, ideas come to fruition and employees experience a good work/life balance. Submit your resume for multiple roles and locations to employment@z6consulting.com! #EnvelopeArchitecture #WeKeeptheOutsideOut ... See MoreSee Less

Adoption of the 2015 IECC has added significant scope by mandating commissioning. This requires that the Building Envelope be commissioned by an independent, third-party consultant that is not directly involved in the design or construction of the building. Learn more from Industry Collaborator David MacLean, Vice President at McMac Commissioning Services, LLC - bit.ly/2AZVZ5W #StrategicPartner #2015IECC #Energycodes #BECx ... See MoreSee Less

Jef Tay Bishop, P.E. discusses how architectural testing provides critical data for engineering calculations as well as finds potential weak points that are either overlooked or impossible to foresee. ... See MoreSee Less

Our team is on-site at the First Lutheran Church Galveston conducting a full building envelope evaluation to remediate moisture issues. We utilized our drone to safely access hard-to-reach areas within the facility to efficiently collect real-time data during our investigation. #Drone #EnvelopeArchitecture #WeKeeptheOutsideOut ... See MoreSee Less

Congrats to Zero/Six Consulting Building Envelope Specialist, Aaron Shaffner who recently earned his Construction Documents Technologist certificate! This achievement demonstrates his thorough understanding of the construction process and a personal commitment to professional development. The greatest leaders are the best students! #ContinuingEducation #CDT #EnvelopeArchitecture ... See MoreSee Less

Connect with us

About

Zero/Six Consulting, LLC is a leader in delivering innovative solutions for the creation and maintenance of better building envelopes. We assemble a dedicated team of in-house professionals — Architects, Engineers, LEED Green Associates, RRO’s, project managers, and field specialists — to meet each project’s particular requirements, performance goals, budgetary criteria, and scheduling requirements, tailoring to the individual building and client needs.
Read More